This section is intended to introduce the reader to various aspects of art, which may be associated with embodiments of the present invention. This discussion is believed to be helpful in providing the reader with information to facilitate a better understanding of particular techniques of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not necessarily as admissions of prior art.
As is well known, current energy demands are primarily satisfied through hydrocarbons, which are becoming harder to find in and extract from the subsurface. Hydrocarbons can be located in formations under all sorts of terrain, including urban environments, wilderness environments, arctic environments, and deep water environments. Moreover, the hydrocarbons can be found in the earth in a variety of forms, including liquid (e.g., oil of a variety of types or qualities) and gas (e.g., methane, etc.) forms. Regardless of the type of hydrocarbon being sought, the present application refers to them all, collectively and individually, as hydrocarbons. Similarly, regardless of where the hydrocarbon may be found, it may be said that the hydrocarbon is found in the subsurface of the earth. Entities in the business of finding and/or extracting hydrocarbon reserves from the subsurface face many challenges, including finding the reserve beneath thousands of feet of rock and, sometimes, water; determining and executing an environmentally and economically practical method of accessing the hydrocarbons; and determining and executing an efficient method of producing the hydrocarbons. While overcoming each and all of these challenges is required for a profitable venture, the technology of the present disclosure relates primarily to methods and systems for finding hydrocarbons in the subsurface. While the discussion herein will not address the challenges of drilling a well, completing a well, operating a well, or the other challenges in providing a producing well, it will be understood that aspects of the present technology may be adapted for use in other phases of the life-cycle of the well.
By way of introduction and background, hydrocarbons are generally found in geologic basins. While some geologic basins formed in the relatively recent past were sufficiently close to the surface to be identifiable by a trained eye on visual inspection, reserves in such basins have been substantially identified and recovered. Accordingly, modern hydrocarbon recovery operations depend on the identification of geologic basins deeper in the earth. Geologic basins are identified through a variety of technologies, including magnetic surveys, gravity surveys, and seismic surveys. Each of these technologies provides important information about the subsurface formations and each provide different types of information helpful in the identification of possible hydrocarbon accumulations. While some survey technologies are considered more complete or more thorough than others, none of the survey technologies will directly or explicitly reveal the location of hydrocarbons or the quantity or volume of hydrocarbons. Thus exploration activities (i.e., efforts to identify new accumulations and/or new prospects) require geoscientists to analyze and/or interpret the survey data to make estimates or predictions regarding the location and volume of hydrocarbons. For convenience herein, the term “geoscientist” is used expansively to include individuals involved in the study of the subsurface to identify hydrocarbons (i.e., individuals involved in the exploration activities), including geologists, geophysicists, engineers, and business executives.
As is well understood, once a geologic basin is identified, the geoscientists must determine whether the geologic basin contains one or more plays, or regions in the subsurface to which hydrocarbons migrated, in which hydrocarbons accumulated, and in which hydrocarbons are stored or trapped. A number of geologic and historical events or conditions are generally believed to be necessary for the existence of a play in a given region of the basin; such events and conditions are referred to as “play elements.” Exemplary play elements include reservoir (porous and permeable rocks where recoverable hydrocarbons may reside), trap (potential hydrocarbon containers), source (organic-rich rocks from which hydrocarbons may be generated), maturity, yield, seal (impermeable rocks that act as barriers to hydrocarbon movement), migration (or viable migration pathways along which hydrocarbon may move from source to reservoir), and timing (having these elements in place in proper temporal relationship to the availability of hydrocarbons). When there is a suitable temporal and spatial confluence of play elements in a substantially contiguous (e.g., regions in fluid communication if not adjacent) geologic volume, geoscientists studying the basin will identify the area as a play. A single geologic basin may include multiple plays, which may be distributed in all three dimensions of the basin. While two plays may be adjacent or near to each other, they may be defined as distinct plays due to varying characteristic in one or more of the play elements.
The division of the geologic basin into one or more plays assists the geoscientists in the conventional next step of identifying prospects within the plays. The term “prospect” refers to regions within the play where an economic quantity of hydrocarbons is believed to exist. Once a play is identified, the study of the basin typically shifts dramatically and tools and resources are focused on the play to identify where within the play a well could be drilled to access the hydrocarbons believed to be within the play region. While a prospect may refer to an actual well intended to intersect a reservoir, prospect-level analysis typically focuses on a finer granularity as compared to play-level analysis but not to the specifics of well trajectory and drilling plans.
It can be seen that the conventional exploration workflow progressively focuses attention on smaller and smaller regions of the subsurface. The subsurface under a large surface area is surveyed to identify geologic basins; the geologic basins are studied to identify one or more plays within the basin; and the plays are studied to identify one or more prospects within the plays. Exploration teams investigating a geologic basin attempt to identify, map, and evaluate all the potential hydrocarbon plays within the basin. Generally, this is done by developing maps of the individual play elements on selected stratigraphic horizons or units. Usually, this work is addressed by sub-teams of geoscientists, each expert in the issues pertinent to a given play element and responsible for data analysis, interpretation, and mapping of that play element. The play-element maps are then combined and examined together for the favorable relationships that suggest a potential play concept. These potential play concepts are summarized in play maps and play summary charts, which form a basis for further evaluation.
This approach, while fundamentally robust in attempting to identify all of the potential plays in the basin, often suffers in practice due to the cost and complexity of developing the play-element maps and the play concepts. During the process of developing the play maps and/or play summary charts, work quickly tends to become focused toward a relatively small number of play concepts that are identified or suspected early in the process. In part, the narrowing focus results from the fact that the analysis, interpretation, and mapping of the individual play elements often requires a high degree of expertise and can be very time-consuming. There is a natural pressure to focus effort toward early-recognized play concepts and avoid interpretation and mapping work for which there is no recognized reward. For example, the early analysis of a basin may reveal that one play element is particularly positive in one region of the basin. The other sub-teams considering other play elements are then motivated to perform their analysis on this region before, and perhaps to the exclusion of, other regions of the basin. While the other regions may be studied, interpreted, and mapped at a later time, this early narrowing focus inhibits full consideration of the hydrocarbon implication of multiple scenarios of basin evolution. For example, information learned through the analysis of one play element in region X of a basin may impact assumptions and/or estimates made in the analysis of a second play element in region Y of the basin. For example, many play element interpretations rely upon understandings or estimates regarding the evolution of a geologic basin and the conditions in the basin over thousands of years. Conclusions regarding some play elements may affect the interpretation of other play elements, such as one evolutionary estimate or theory for a first play element interpretation being inconsistent with an evolutionary theory applied for an interpretation of a second play element.
Additionally, while the play-element maps and play maps produced with this early, narrowed focus describe and delineate the early-identified play concepts very well, they are of limited value in helping the exploration team recognize additional play concepts that may exist in the basin. Additionally, as information regarding the basin is updated through exploration, development, and production operations, this information is generally not incorporated back into the play element maps and play maps for the entire basin due to the cost and complexity of updating the play element maps even though the implications of the information are understood to potentially affect the entire basin. For these and other reasons, creativity or serendipity continues to discover hitherto unsuspected plays in basins of even advanced exploration maturity.
Accordingly, the need exists for systems and methods to allow geoscientists to perform basin-level study of play elements to identify play concepts in the basin. Additionally or alternatively, systems and methods are needed to render the basin-level and play-level studies more economical to facilitate the basin-level analysis and to facilitate the repetitive updating of the basin-level and play-level studies. The technologies in the present disclosure are believed to satisfy, at least in part, one or more of these needs.
Other related material may be found in at least U.S. Pat. No. 7,043,367. Further, additional information may be found in U.S. Patent Publication No. 2007/0203677 A1; and International Patent Publication No. WO 2006/016942 A1. Still further, additional information may be found in W. A. Heins & S. Kairo, Predicting Sand Character with Integrated Genetic Analysis, Geological Society of America Special Paper 420:345-379 (2007); and K. C. Hood et al., Use of Geographic Information Systems in Hydrocarbon Resource Assessment and Integrated Opportunity Analysis in Geographic Information Systems in Petroleum Exploration and Development (T. C. Coburn & J. M. Jams eds), AAPG Computer Applications in Geology 4:173-186 (2000).